PrivtPilotRadarTech
Yes, I see what you're saying. When I did the calcs months ago I did them off a chart and 240nm looked about right, but if we were to assume an altitude of 35,000 feet the radar horizon would be 293nm according to the calculator at
Horizon calculator - radar and visual.
However the line of sight does come in at 243nm and I can wonder if the Pulau Penang Radar was seeing or set to include the extra distance provided radio waves by atmospheric distortion. My hands on experience with radar ended when I got out of the Army in the 60s, so I don't know details of operation of phased array stuff.
Another issue is of course what altitude 9MMRO was at as it exited Pulau Penang Radar coverage; it might have been lower than my original assumption (that it had recovered any altitude lost earlier and was at the most efficient altitude for max range.) It might have been lower for one reason or another (possibly to avoid being tracked by the Thai radar at Hat Yai or to keep a low profile towards Indonesian ATC or military radar.)
The fact is that we don't know some of the specific details regarding the flight, so striving for exact precision is currently beyond our reach. I see the matchup with the Inmarsat 18:29 ping ring as being as perfect as we could hope for. I was astounded when I made the first plots in the western part of the strait and saw how close the two sources lined up.
Yes you are correct about tensions in the region. The Malaysian and Indonesian navys are in an adversarial relationship as far as I can see. And the Thai are dealing with radical fundi Muslim attacks among other things. I have no doubt that both the Thai and Indonesians have radar tracks of 9MMRO's flight stored in their "secret" files. These are very unlikely to ever see light of day.